Automatic slack adjuster



July 20, 1954 J. R. SNYDER 2,684,132

AUTOMATIC SLACK ADJUSTER Filed Nov. 19, 1948 4 Sheets-Sheet l July 20,1954 J. R. SNYDER AUTOMATIC sLAcx ADJUSTER 4 Sheets-Sheet 2 Filed Nov.19, 1948 mm. 5 V X w u/f @L E .M W2,

@Wmme July 20, 1954 J. R. SNYDER AUTOMATIC sLAcK ADJUSTER- 4Sheets-Sheet 3 Filed Nov. 19

July 20, 1954 J. R. sNYDER AUTOMATIC sLAcx ADJUSTER 4 Sheets-Sheet 4Filed Nov. 19, 1948 QNX INVENTOR. 1605 /Pz/.s/f .5m/0H? BY #Mam ,E mw, M

7 GENEVE Patented July 20, 1954 UNITED vSTATE T OFFICE AUTOMATIC SLACKADJUSTER Jacob Rush Snyder, Cleveland, Ohio Application November 19,1948, Serial No. 60,946

(Cl. 18S-203) 14 Claims. l

This invention relates to devices for automatically taking up slackwhich may develop in the rigging of braking apparatus due to wear on thebrake shoes or from other causes and, 'as one of its objects, aims toprovide an improved device of this kind.

Another object is to provide an improved slack adjuster in whichrelative rotation between cooperating screw members for taking up theslack is produced by novel cam means which is actuated by thebrake-applying and brake-releasing movements. I

A further object is to provide an improved slack adjuster of thischaracter in which the cam means is actuated preliminarily during thebrakeapplying movement so as to render the device effective to causeslack to be taken up during the brake-releasing movement.

Still another object is to provide an improved slack adjuster of thecharacter mentioned, in which novel means is employed for rendering thetake-up action of the screw members ineffective at the end of apredetermined relative travel.

As another of its objects this invention provides an improved slackadjuster in which the slack adjusting mechanism is contained in thehousing of a brake cylinder device.

Yet another object is to provide an improved slack adjuster of the typereferred to, in which one of the cooperating screw members is carried bya push rod which projects from the brake cylinder for connection withthe rigging and the other is actuated by the piston of the brakecylinder.

A further object is to provide an improved slack adjuster of thecharacter mentioned, in which the cam means for producing` the slacktake-up action is actuated by axial movement imparted to one of thecooperating screw members by the piston oi the brake cylinder.

Still another object is to provide a combined brake cylinder device andautomatic slack adjuster in which the piston rod of the brake cylinderconstitus one of the cooperating screw members for taking up the slack.

Another object of the invention is to provide a combined brake cylinderand automatic slack adjuster in which the piston rod is hollow andinternally threaded., and a push rod extending into the hollow pistonrod carries a screw member which cooperates with the internal threadthereof.

As a further object this invention provides an improved mechanism of thecharacter mentioned, in which one of the cooperating screw members 2 isconnected with the piston and is rotatable relative thereto for causingthe screw members to take up slack in the brake rigging, and in whichcam means acts to produce the rotation of said one screw member duringthe operation of the piston in the brake cylinder.

It is likewise an object of the present invention to provide an improvedmechanism of the character referred to, in which the cam means comprisessets of cam and cam follower elements oi which one set is connected withthe rotatable screw member and the other set is connected with thehousing of the brake cylinder'.`

A further object is to provide an improved mechanism of the characterreferred to, in which the connection for one set of the cam elements ismade through a lost-motion device which is actuated during thebrake-applying stroke of the piston to render the cam means effective inproducing relative rotation of the screw means for taking up slackduring the return Stroke of the piston.

It is also an object of this invention to provide an improved slackadjuster of the character mentioned, in which the take-up mechanism canbe readily reset by manual adjustment from the outside of the housing orbrake cylinder after a predetermined travel of the take-up mechanism hastaken place.

Other objects and advantages` of the invention will be apparent from thefollowing detailed description and in the accompanying sheets ofdrawings in which:

Fig, 1 is a longitudinal sectional view taken through a combined brakecylinder device and automatic slack adjuster and which embodies thepresent invention;

Fig. 2 is a partial transverse sectional view takeny through the cammeans of the slack adjuster, as indicated by section line 2 2 of Fig, 1;

Fig. 3 is a partial transverse sectional view taken through thelost-motion device associated with the cam means, as indicated bysection line 3 3 of Fig. 1;

Fig. 4 is a development View showing the cam grooves; 1

Fig. 5 is a fragmentary longitudinal sectional view corresponding with aportion of Fig. 1 and showing the cooperating screw members on a largerscale;

Fig. 6 is another fragmentary longitudinal secm tional viewcorresponding with aportion of Fig. l and showing the cam elements on alarger scale;

Fig'. 7 .is another such fragmentary longitudinal sectional View showingthe lost-motion device on a larger scale Fig. 8 is a fragmentaryelevation showing a portion of the push rod which has certain keywaystherein;

Fig, 9 is a partial transverse section further illustrating the keys andkeyways of the push rod taken substantially as indicated by section line-S of Fig. 5;

Fig. 10 is a fragmentary elevation view shown ing an interlock providedbetween the brake cylinder and the push rod;

11 is a longitudinal section sirnilal` to Fig. l but showing a modifiedform of combined brake cylinder device and automatic slack adjuster;

l2 is a fragmentary longitudinal section corresponding with a portion ofFig. 11 and shown ing the releasable connection for one of the screw mesers on a larger scale and with the keys of the connection fully engagedin their keyways;

Fie. 13 is a fragmentary view, partly in longitu al section, furtherillustrating such releasable connection and showing the keys partiallywithdrawn from the keyways.

Fig. le is a transverse section taken on the irregrier section lineid-ifl of Figs. 11 and 13;

i is a fragmentary longitudinal section corresponding with anotherportion of Fig. 11 and showing the cooperating screw members andassociated parts on a larger scale;

Fig. 16 is a partial transverse section taken on line l-i of Figs. 11and 15;

Fig. 17 is a partial transverse section taken on line lli-il of Figs. 1land 15;

Fig. 1S is a partial transverse section taken through the cooperatingcam elements, as indicated by line iS--EB of Fig. 1l;

i9 is a development View of the sleeve which carries the cam grooves;

20 is a side elevation showing a connecting member and torsion springassembly unit in detached relation; and

21 is an end view of the externally threaded screw member showing thelocation of the stop pin carried thereby.

In the two embodiments of the invention illusm tr .ted in the drawingsan automatic slack ad- Ing mechanism is shown embodied in a brakecylinder device, and although the embodiment of a slack adjustingmechanism in a brake cylinder device constitutes one important featureof this invention, it should also be understood that the slaci:adjusting mechanism is considered to be novel in itself and adapted tovarious other applications. For example, the slack adjusting mech anismcould be used in an installation in which it would be located externallyof the brake cylinder device or could be located in a housing other thanthe housing of a brake cylinder device.

Froceedingrst with a description of the embodiment of the inventionillustrated in Figs. 1 to li) inclusive, the drawings show an automaticslack adjusting mechanism il) located in a brake cylinder device il. Thebrake cylinder device l comprises a housing i2, which in this instanceis formed of connected housing sections 12a and 52h, and a piston i3reciprocably operable in the housing. The piston i3 is axially movablein the housing i2 and has an axial guide stem i4 which telescopicallyreceived in a tubular extension of the housing section lia. The guidestem is shdable in a bushing i6 which is mounted in the extension l5 andretained therein by the snap ring iba.

The piston i3 cooperates with the housing seotion 52a in dening achamber il' to which pressure uid, such as compressed air, can. suppliedthrough the connection i8. lThe piston can be slidable in the housing i2but preierably, as here shown, the seal between the piston and housingis formed by a so-called rolling diaphragm it which is of asubstantially sleeve-like form. This diaphragm can be made of anymaterial suitable for this purpose, such as a rubberized iabric, andpreferably has beads Hic and isb extending therearound at its inner andouter ends. The diaphragm, or at least the bead its thereof; ispreferably elastic in character.

The inner end of the diaphragm IS is suitably attached to the piston i3as by a clamping means or by havingl the bead ld in an elastic C,rippingengagement with an inwardly oiset shoulder 28 provided on the piston.Because oi the elastic character of the diaphragm material, the bead itcwill contract tightly around the piston so as to cooperate with theannular shoulder forming a huid-tight connection at this point. Theouter end of the diaphragm is anchored on the housing i2 and is influidutight engagement therewith by having the bead io clamped betweenthe housing sections iZc and 12b. ln ad dition to the sealing actionproduced by the elas tic gripping oi the shoulder 26 by the bead icc,the intermediate portion of the diaphragm i3 will also be sealinglypressed against a substantiai portion of the length of the skirt of thepiston by the uid pressure in the cylinder chamber il. Since the rollingsleeve diaphragm l@ forms seal in which there is no sliding or rubbing`ci the parts, no lubrication will be needed auf` eiiicient operatingcondition will be mainta for a long period of troubleiree service.

The piston i3 may be oi any suitable construction, for example and ashere shown, the body lSa of the piston may be in the form of a drumshaped` metal member having a substantially central opening i327 thereinin which the inner end of the hollow guide stem It is secured by thewelding indicated at 2i. The piston may also include a flat ring-shapedmember which forms a thrust seat and whose inner face pre vides a plainor friction bearing surface ior a purpose hereinafter explained. Themember has its outer and inner edges connectedrespec tively with thepiston body i3d and the inner en of the guide stem M by the welds Till.prevent the diaphragm i9 from being subjec to any torsional stresses thepiston i3 is prefoably held against rotation in the cylinder housii l2as by means of the guide sleeve iii-c which is connected with the pistonand is slidable on guide rod I2C carried by the housing.

The slack adjusting mechanism lo is located in the chamber 25 of thebrake cylinder housing i2 and which chamber is vented to atmospherethrough one or more breather openings provide: with suitable strainers25. The slack adjus mechanism comprises two cooperating relativelyrotatable screw members 2l and 23 which are posed in coaxial relation toeach other and to the brake cylinder housing. l2. A push rod 2S tendingaxially of the housing orms a part or" the brake cylinder device li aswell a part ci? the slack adjusting mechanism i3. The .f end of the pushrod 29 has the screw mem'ce l mounted thereon in the manner hereinaftereX plained and its outer end projects from the housing I2 and carries aclevis 39 which is adapted for connection with the brake rigging (notshown),

The slack adjusting mechanism li! further includes a sleeve 3l extendingin coaxial surrounding relation to the push rod 2i! and having its innerend in telescoping relation to the adjacent end of the screw member 23,The outer end of the sleeve 3i is connected with thel housing l2 by alost-motion device 32 which will be further described hereinafter. Asan' important part thereof the slackadjusting mechanism lil alsoincludes sets of cooperating cani elements 33 and 34 carriedrespectively by the screw member Z and the inner end of the sleevetl andwhich cam elements will also be :further described hereinafter.

The screw member 23 is here shown in the form of a hollow rod having aright-hand internal thread 28o therein and also having a substantiallyradially projecting annular ila-nge 35 thereon at an intermediate pointof its length which seats against the friction bearing surface 22a ofthe thrust member 2t of the piston i3. The flange 35 continuously heldin seating engagement with the bearing surface 32o by a compressionspring 3S which is disposed in surrounding coaxial relation to the pushrod 2s and the sleeve 3i. This spring is of suicient strength to providethe necessary force for producing a return movement of the pistonfollowing an application of the brakes and to cause the brakereleasingmovement to be transmitted through the rigging to the brake shoes. Theright-hand end of the spring 35 is in sea .lng engagement with the endwall of the housing section i219 and its other end engages a suitablespring seat such as the dished member it? which cooperates with theflange 35 of the hollow rod 28.

The hollow rod 23 is, at times, referred to herein as an actuatingmember because of the manner in which it cooperates with the screwmember 2l in imparting a slack take-up movement to the push rod 29 andis also at times referred to as the piston rod of the piston it. Thehollow rod 23 is not rigidly connected to the pi"- ton i3 but isconnected therewith through the pressure relation with which the nan-ge35 is held against the friction bearing surface 22a of the thrust member22 by the compression spring S and by the brake-applying force developedby the piston. lit is important to note that the hollow rod or screwmember 23 is rotatable relative to the piston ll during the returnstroke thereof for imparting the slack taire-up movement to the screwmember 2'! and the push rod 2Q, as will be further explainedhereinafter. The lefthand end of the hollow rod 2t extends through thehead portion [3o/of the piston and into the hollow guide stem id and isrotatably journalled in the latter by means of the axially spaced bueh-33 and 3S.

it is desirable that the hollow rod 28 be relatively freely rotatableduring the return stroke of the piston t3 and accordingly ananti-friction bearing member such as the dat annular bearing member @Elis provided between the radial flange $55 and the spring seat Si?. It isdesirable that the hollow rod Zit be held against rotation during thebrake-applying stroke of the piston i3 and this is accomplished by theaction ci the abovementioned friction bearing surface 22a on the angeCiti. The spring 3l is preferably held against rotation at all. timesfor this purpose, is provided with an axial ci which extends into anopening i2 in the thrust member 22 of the piston.

The screw member 2l' has a right-hand external helicaly thread 27a.thereon which cooperates with the internal thread 286/, of the hollowrod 2t. The screwmember 2. is preferably in the form oi a sleeve"y whichis connected with the inner end of the push rod 2S by being mounted on areduced stem extension or spindle portion i3 thereof. The end of thestem extension 'it is threaded and provided with a retaining nut i3dwhich retains the screw member 2 in adjacent relation to the shoulderfili of the push rod without applying a clamping force which wouldprevent rotation of the screw member on the stem extension.

The engagement of the thread 2id of the screw member 2lwith the internalthread 28ar of the hollow rod 23 forms a thrust transmitting connectionbetween these members by which axial movement is imparted directly tothe push rod d during the brake-applying and brake-releasing functions.This engagement between the threads of the members 2l and 28 also formsa crew connection by which axial movement is imparted to the push rod 2efor taking up slack in the rigging in response to rotary movementimparted to the hollow rod 23 by cam means comprising theabove-mentioned cani elements 33 and 35i and which cam means will beiur-ther described hereinafter.

A connection i5 is provided between the screw member and the push rod 29in the form or" an automatically releasable connection which at timeswill permit this screw member to be rotated idly on the stein extension513 of the push rod. This is desirable for preventing damage to theapparatus when the screw member 2i' approaches or reaches the end of itsslack taire-up travel along the hollow rod 2g as represented by the stopor bushing 28h which is secured in the hollow rod as by means of the pin2do. This automatically releasable connection 635 includes a pair ofkeys 0,6 which extend into a pair of keyways il provided in the push rod2S? adjacent the shoulder lid thereof. The adjacent end the screw member21 is likewise provided with a pair of keyways i8 in which the keys ci@also engage. The keys l project from the lreyways i3 of the screw member2l into the keyways i? of the push rod 29 for normally connecting screwmember with the push rod and the keys are held in this projectedrelation by a compression spring di? disposed around the reduced portionZ'Ib in which the kei/ways s@ are located.

The connection l5 also includes a sleeve 5@ which is disposed insurrounding relation to the reduced portion Ela so as to form a housingfor the spring d and the keys dii, and which also 'forms a stop ashereinafter explained. The lefthand end of the sleeve 5o is providedwith an inturned annular ange or bead 5l forming a seat i'or the spring9 and which flange is normally held against an annular shoulder 52 ofthe screw member 2l? by the action of this spring. As shown in thedrawings, the sleeve 5o is of a length such that its other end overlapsthe push rod 2S and extends a short distance beyond the shoulder 44.

The keyways c? of the push rod 29 are of uniform width :for the majorportion of their length, as shown in Fig. 8, and have substantially fiatparallel sides 53 and 54. The sides 53 form flat faces which extend forsubstantially the ruil length of these keyways whereas the side facesdii at the opposite side of these keyways are provided at their outerend with a bevel 55 extending at an angle to the axis of the push rod,for

example, an angle of about forty-five degrees. When the screw member v2lapproaches or reaches the end of its slack take-up travel along thehollow rod 28, the inner ends of the keys 46 engage the bushing 28h andthe keys are pushed outwardly of the keyways 4'! until the bushing isengaged by the inner end of the thrust sleeve or stop 5e. The inner endsof the keys 46 will then lie opposite the bevel faces 55 and thereafterany tendency for the hollow rod 28 to rotate the screw member 21 in aclockwise direction will cause the inner ends of the keys to engagethese bevel faces and to be cammed outwardly thereby to fully disengagethe keys from the keyways lil. Thus when the screw member 2l reaches theend of its slack take-up travel, the keys llt and the bevel faces 50become effective as a ratchet means which automatically disconnects thescrew member 2l from the push rod 2s and permits this screw member to berotated idly on the stem 43a.

As explained in greater detail hereinafter the push rod 2s is adapted tobe manually rotated in a clockwise direction for resetting the slackadjusting mechanism Ill by returning the screw member '2l to its initialposition after it has completed its slack take-up travel. Since theinner ends of the keys d6 normally remain partially engaged in thekeyways lll any such clockwise rotation of the push rod 29 will causethe straight side faces 53 of these keyways to cooperate with the keysand impart rotation to the screw member 21. As soon as the screw member2l moves away from the bushing 2gb the keys le will be fully engaged inthe keyways dl by the spring 49.

The cam means referred to above as comprising the sets of cooperatingcam elements 33 and effi serves to impart rotation to the hollow rod 28during the return stroke of the piston i3 so as to cause the internalthread 28a to cooperate with the screw member 2l for imparting axialmovement to the push rod 29 in a direction to extend the latter from thebrake cylinder housing l2 and take up slack in the brake rigging. Thecam elements 33 comprise relatively steeppitch threads or cam groovesformed in the outer surface of the hollow rod 28 and the cam elements 34comprise substantially radially inwardly extending pins which engage inthese cam grooves and constitute cam followers.

The cam grooves 33 of the hollow rod 28 are further illustrated in thedevelopment View of Fig. 4 from which it will be seen that the hollowrod 23 provided with two such grooves in substantially diametricallyopposed relation and that each of these grooves comprises twosubstantially helically inclined groove portions 56 and 5T and asubstantially axially extending straight groove portion 58. Theinclination of the groove portion 51 is such that it converges towardthe groove portion 5B and the adjacent ends of these groove portions areconnected with each other by a substantially circumferentially extendingtransfer passage 59. The transfer passage 59 also serves to connect theend of the inclined groove portion 55 with the adjacent end of thestraight groove portion 58.

The cam followers 34, as mentioned above, are in the form of pins whichextend substantially radially inwardly from the sleeve 3l and engage inthe cam grooves 33. The pins Sie can be mounted on the sleeve 3| byproviding the latter with a ring-member 60 which is welded thereto andis disposed in surrounding relation to the vice s2.

hollow rod 28 and in which ring-member the pins are mounted by means ofneedle bearings lil. When mounted in this manner the pins 3d will becapable of rotation about their axes and will cooperate with the sidesof the cam grooves 33 in the manner of rollers with a minimum amount offriction. As will be presently explained in greater detail, the pins 34constitute reaction members which, when held by the sleeve il fromrevolving around the axis of the push rod 29, will produce rotation ofthe hollow rod 23 when the latter is moved axially relative to thesleeve 3l.

The right-hand end of the sleeve 3l is connected with the end wall ofthe brake cylinder housing member 12b, as mentioned above, and thisconnection embodies the lost-motion device 32 which will be describednext. The housing section [2b is provided at this point with a bearingmember 62 through which the push rod 2E extends. The bearing member t2may be connected with the housing section 52h by the welding 63 and isprovided with a bushing Se in which the push rod is slidable. A suitablepacking or dirt seal 65 is provided in the bearing member $2 adjacentthe outer end of the bushing iid and in surrounding relation to the pushrod 29. The packing t5 is retained in place as by means of the snap ring66,

The bearing member B2 is provided with a pair of substantially radiallydisposed stop pins el which constitutes a part of the lost-motion de-These pins are mounted in xed relation in the bearing member 62 but havetheir outer ends projecting radially therefrom. The right-hand end ofthe sleeve 3! extends in surrounding telescoping relation to the bearingmember 62 and is journalled thereon for rotatably supporting this end ofthe sleeve in coaxial relation to the push rod 2e. This end of thesleeve 3l can be reinforced as by means of short tubular member 6smounted thereon and welded thereto, as shown in Fig. '7. This journalledouter end portion of the sleeve 3i is pro vided with a pair ofcircumferentially extending slots E9 in which the outer ends of the stoppins lll' engage. The slots 69 cooperate with the pins Si in forming thelost-motion connection by which the sleeve 3| is permitted to havelimited rotary movement around the push rod 2Q.

For controlling the cooperation between the cam elements 33 and 3d, itis desirable that the sleeve 3l be rotated automatically in acounterclockwise direction (as seen in Fig. 3) after it has beeninitially rotated in a clockwise direction by the axial movementimparted to the hollow rod 28 by the piston i3 during the brake-applyingmovement of the latter. For this purpose a torsion spring lil isdisposed in surrounding relation to the bearing member E2 and the.iournalled end of the sleeve 3l. This torsion spring has an inturnedringer or hook lc on one end thereof which engages in a slot li of thebearing member S2 for anchoring this end of the torsion spring on thebearing member. The opposite end of the spring 'ril has a similarinturned finger or lug 'ith which engages in a hole provided in the ringmember t8 of the journalled end of the sleeve 3l.

When clockwise rotation is imparted to the sleeve 3l by the hollow rod28, as is permitted by the slots 69, the torsion spring 'it will betensioned and when the sleeve 3l is subsequently released the force ofthe spring will rotate the sleeve in a counter-clockwise direction totake up the lost-motion afforded by the slots 59. The

torsion spring l thus moves ythe ends 69a of the slots te intoengagement with the 4stop pins el so that the pins thereafter hold thesleeve 3| against further counter-clockwise rotation and provide a solidconnection between the sleeve and the brake cylinder housing againstwhich the sleeve can react.

ln the operation of the above described combined cylinder device andslack adjusting mechanism, pressure fluid is supplied to the brakecylinder` chamber il through the connection I8 and acts on the piston i3moving the latter to'- ward the right as seen in Fig. l. This movementof the piston is transmitted to the hollow rod 2t through the flange t5thereof and, because ci the threaded engagement between the screwmembers 2l and 23, the push rod il will also be moved toward the right.This right-hand axial movement of t. e push rod 29 is thebrake-ap plyingmovement and causes a braking force to be supplied to the brake shoesthrough the rigging. t

.at the beginning of the brake-applying movement of the piston it thecam follower pins 3d are located adjacent the right-hand end of the camgroove portions 5t, as indicated in Fig. 4'. During this brake-applyingmovement of the piston it and the hollow rod 23, the side faces 5ta ofthe cani groove portions e8 exert a wedging action on the pins Se andcause the above-mentioned initial rotation to be imparted to the sleeveSi in a clockwise direction as seen in Fig. This clockwise rotation oithe sleeve 3i causes the torsion spring li! to be tensioned, as eX-lained above. During this brake-applying movement it will be understood,of course, that the hollow rod 2li will be held against rotation by theirictional engagement provided between the flange 35 and the thrustmember 22 of the pils-y ton. The axial movement of the hollow rod 28toward the right by the piston I3 will cause the pins Sli to advancerelatively along the groove portions 5Fl toward the transfer passagesEtf .y

in come cases the brake-applying movement will of such extent that thepins 34 will have i i.Vance and return movement entirely within thelength oi the groove portions' and in those cases no relative rotationwill be produced between the screw members 2i and 23 and no slacktake-up action will result. lThis condition of operation is likely tooccur when the` brake shoes are new or relatively thick and there islittle or no slack in the brake rigging. When the operating condition issuch that the pins 34 operate entirely in the cam groove portions 56, asjust described, the effect produced by the coop-v erating cam elements53 and .lll is merely to cause rotation of the sleeve til within thelimits permitted by the slots Si! of the lost-motion connection 222.

When the brakeapplying operation is such that the axial movement of thehollow rod 28 is of suiiicient length as to cause the cam follower pinsSli to advance as far as the transfer pas- 5i?, the pins will travelover the points or control projections 'l2 of the caniy grooves and willthereupon be released so as to permit the sleeve Si to be rotated in acounter-clockwise `direction (as seen in Fig. 3) by the' torsion springle. The action of this spring will be to cause the pins 3e to be rapidlymoved through the transfer passages 5S into engagement with the sidefaces 58a of the groove portions 58. If the brake-applying movementcauses further axial movement or the hollow rod 28 toward theY right,

the pins 34 will simply advance further along the straight grooveportions 58. if desired one of the control projections, for example theproiecn tion l2a, can be made longer than the other so that only thisrelatively longer projection will control the movement of the pinsthrough the transfer' passages 59.

When the brakes are released, fluid pressure is exhausted from the brakecylinder chamber il permitting the compression spring S5 to impart areturn movement to the piston i3 and a brakereleasing movement to thehollow rod 2S and the push rod it. During this brake-releasing operationthe movement of the hollow rod 2t toward the left causes the camfollower pins Eli to travel relatively in a return direction along thestraight groove portions 58 toward the right as seen in lFig. e, and tothen enter the cam groove por- 5l. During this return relative movement,the pins 3e exert a wedging action against the side iaces Sla of thecani groove portions 5l' to thereby impart a counter-clockwise rotation(as seen in Fig. 2) to the hollow rod 28. It will be understood that atthis time the sleeve 3l is held against rotation by the stop pins Si' ofthe lostmotion connection 32 and the sides Sla of the inclined camgroove portions 51 reacting against the then stationary cam followerpins 36 cause such counter-clockwise rotation of the hollow rod 28. Thiscounter-clockwise rotation of the hollow rod 28 causes the internalthread 28a thereof to advance the screw member 2l' toward the rightthereby shifting the push rod 29 in an outward axial direction fortaking up slack in the brake rigging. At the end oi the return stroke ofthe piston i3 the cam follower pins 3d will occupy their initialrelative position shown in Fig. d and the mechanism will be ready foranother such cycle the next time that the brake cylinder device i i isoperatedto apply and release the brakes.

The range of operation for the mechanism it in taking up slack in thebrake rigging corresponds with the eiective length of the internallythreaded portion of the hollow rod 2t. When the functioning of the slackadjusting mechanism i has taken place to the extent of causing the screwmember 27 to be advanced along the hollow rod ,2li to the inner endthereof, the connection fit between the screw member 2l and the push rod2li is automatically released, as explained above, to prevent damage tothe apparatus. The above-described releasable connection formed betweenthe screw member 2l' and the push rod 29 by the key and keyway elements:l5 and il? accomplishes this purpose. Thus when the slackadjustingrelative rotary movement between the screw members 2l and 28 advancesthe member 2l to 'the bushing 2th this bushing is engaged by the innerends of the keys ed and shifts these keys in an axial direction to theposition in which their inner ends cooperate with the beveled portions55 to form a ratchet, as previously exe plained herein. The screw member2l is then free to rotate idly with the hollow rod 2t and relative to'the push rod 29v so that no further slack adjusting movement will beimparted to the push rod.

When all or thesiaclr adjusting travel between the screwl members 2 and28 has been utilized, the slack adjusting .mechanism l@ remains in thecondition with the screw member 2l located adjacent the bushing 23h andwith the cooperating key and keyway elements 46 and il producing theabove described ratchet action which permits rotation of the hollow rod28 by the cam 11 means without imparting further axial slack adjustingmovement to the push rod 29. When the mechanism is in this condition itshould be manually reset and, in accordance with another of the featuresof this invention, the apparatus is designed to permit such manualresetting. To reset the apparatus the brake rigging is disconnected fromthe clevis 3Q and the push rod 29 is rotated in a clockwise direction byapplying a rotative force to the clevis.

The clockwise rotation of the push rod 29 causes the dat side faces 53of the keyways @l to cooperate with the end portions or" the keys 45 andimpart an initial clockwise rotation to the screw member 2l. The springla thereupon reengages the `keys for their full extent in the keyways,as mentioned above, to thereby reestablish the normal drive connectionbetween the push rod and the screw member 2l. Further clockwise rotationoi' the push rod 2Q will cause the screw member il to advance toward theleft in the hollow rod 28 thereby retracting the push rod into the brakecylinder l2 to substantially the position in which it is shown in Fig.l. The apparatus will then be ready for further slack-adjusting serviceand the brake rigging is thereupon reconnected to the clevis 3l).

During the resetting of the slack-adjusting mechanism le, as justdescribed, it is desirable to prevent the screw member 2l from exertinga pulling force on the hollow rod 28 such as might cause compression ofthe spring 3e and shifting of the piston i3 part way along its workingtravel. For this purpose an interlock is provided between the clevis itand the brake cylinder l2 and which becomes effective when the screwmember 2l has been fully returned to its initial position. in thisinstance the interlock comprises a pair of stop shoulders or teeth l5 onthe outer end or" the bearing member and a second pair of such shouldersor teeth l5 on the clevis 36. When the clockwise resetting rotation or"the push rod has retracted the push rod into the brake cylinder to thepoint where the teeth l of the clevis engage the teeth 'i5 of thebearing member E2, further rotation of the push rod will be prevented bythe interlock and the screw members El and t will be prevented fromloading the spring 36 and imparting an initial travel to the piston i3.

Figs. ll to inclusive, illustrate a modiiied form oi" combined automaticslack adjuster and brake cylinder device 89 which will now be describedand which embodies the same general features and principles as the abovedescribed device lli oi Figs. l to l0 inclusive. The modiiied apparatuscomprises in general, a brake cylinder device tl consisting of a housing82 and a piston 33 operable therein and an automatic slack adjustingmechanism Se which is located in such housing. The brake cylinder device3l also includes a push rod t5 having one end thereof projecting fromthe housing S2 and carrying a clevis t by which it is adapted to beconnected with a brake rigging. Additionally, the brake cylinder deviceincludes a compression spring 3l which is located in the housing insurrounding coaxial relation to the push rod 85 and which causes thereturn stroke of the piston and push rod during the releasing of thebrakes.

The housing 82 of the brake cylinder device 8i can be of a sectionalconstruction similar to that of the housing l2 already described aboveand has a huid pressure chamber or cylinder 88 therein in which thepiston 83 is operable. The housing 82 is provided at one end thereofwith a iixed hollow bearing member t?) carrying a bushing 89a in whichthe push rod is slidable and through which one end of the push rodprojects for connection with the brake rigging. An axial sleeve el!extends into the housing 82 in surrounding relation to the push rod andis connected in fixed relation to the housing by having its outer endattached to the bearing member 3E as by means of the welding indicatedat el. At its opposite end the housing S2 is provided with a hollowaxial guide projection 92 having a bushing t3 mounted therein.

The piston t3 is provided with head and skirt portions 33a and 83h andis movable through a brake applying stroke by pressure huid, such ascompressed air, supplied to the chamber 8l through the connection 93. Arolling sleeve diaphragm 95 having one end anchored on the housing 32and its other end mounted on the piston 53 forms a seal between thepiston and housing. The piston 83' is provided on one side thereof withan axially extending hollow guide stem 9'! which extends into the hollowguide projection 92 of the housing and is slidable in the bushing 93. Onits other side the piston is provided with another axially extendinghollow guide stem 98, the outer end of which extends into telescopingrelation with the xed sleeve B of the housing. A bushing 99 carried bythe inner end of the fixed sleeve 9i) is slidably engaged by the hollowguide stem 98, the bushing being mounted on the outside of the fixedsleeve and the guide stem extending in telescoping relation around thebushing and sleeve. With the construction just described, it will beseen that the piston 83 is supported and guided in the housing 82 by theslidable engagement of the guide stems El' and @3 with the bushings 93and 99. It will be observed also that the guide stems 91 and 93 form apiston rod for the piston and provide a passage or chamber which extendsaxially through the head of the piston.

The slack adjusting mechanism 8d forms an operative connection betweenthe piston t3 and the push rod 85 and includes a pair of cooperatingscrew members lill and lil?. The screw inember lill is an internallythreaded hollow member carried by the piston 33 and located insurrounding coaxial relation to the push rod The screw member m2 is anexternally threaded member mounted on the push rod 85 and which engagesin and extends through the internally threaded screw member ll. Thesescrew members lll! and |92 cooperate in forming a direct thrusttransmitting connection between the piston 83 and the push rod 85 bywhich brake applying movement can be transmitted to the latter during aworking stroke of the piston. These screw members also provide aconnection between the piston and push rod such that when one of thescrew members, in this instance the member itil, is rotated in aclockwise direction, as seen in Fig. 17, outward axial movement will beimparted to the push rod 85 for taking up slack in the brake rigging.

For the accomplishment of the slack take-up action just explained, thescrew member is! is rotatable relative to the piston 83 and relative tothe screw member m2. The screw member lli! is mounted on the piston 83by means of an outer bearing race H33 which is located in the guide stem98 and an annular row of anti-friction bearing elements i011 by whichthis screw member is supported in this outer race. The connectionbetween the rotatable screw member lill and the piston 83 also includesa substantially spherical thrust seat |95 carried by the piston and anend thrust face llil engaging the same and carried by the screw member.The thrust seat |05 can be formed directly on the piston 83 or on a ringmember Hita., as shown in this instance, and which ring member isincorporated in the piston by being welded to the guide stems Sl and 08.

By mounting the screw member on the piston 83 in the manner justexplained, it will be seen that during a working stroke of the pistonthe thrust will be transmitted to the push rod 85 directly through thethrust surfaces |05 and i 05, and since these surfaces are only plainbearing surfaces, there will be some friction therebetween which willtend to hold the screw member 50| against rotation during such workingstroke. The return stroke of the piston is produced by the compressionspring 8l and during this return stroke the thrust of the spring istransmitted to the piston through the anti-friction bearing elements t.Since the bearing load at this time is substantially removed from thethrust surfaces m and |06 and there will be very little friction betweenthe screw member lili and the bearing elements lcd, this screw memberwill be free to rotate relative to the piston during the return strokeof the latter.

The screw member |02 is here shown in the form of a relatively longsleeve which is mounted on a reduced stem or spindle portion lill of thepush rod 05. At the base of the stem portion lill, the push rod isprovided with a shoulder |03 against which one end of the screw member|02 engages for transmitting thrust to the push rod. At the other end ofthe screw member |02 a releasable connection, indicated generally by thereference character |09, is provided between this screw member and theend of the reduced stem portion iii'l of the push rod. This releasableconnection serves to connect the screw member |02 with the push rod andwhen the screw member ist has substantially traversed its permissibletravel in the screw member Icl, this connection releases the screwmember |02 so that it can rotate idly relative to the push rod. Thescrew member |02 will then impart no further axial movement to the pushrod until the mechanism has been manually reset. This releasableconnection therefore prevents damage to the slack adjusting mechanism8f3 when this mechanism has operated to take up slack to the extent ofits full operating capacity.

The releasable connection Ille is formed by a pin l il which extendsthrough the stem |01 aoljacent the end thereof and a collar ||2 which isaxially shiftable on the stem itl and carries a pair of substantiallydiametrically opposed axially extending arcuate keys H3. The end of thescrew member |02 is provided with a pair of diametrically opposedkeyways H4 into which the keys H3 extend, as shown in Fig. 13. Thecollar il? includes a sleeve portion l2@ which is sidable on the stem|01 and a radial flange or disk portion il??? on which the keys H3 areformed or mounted. The sleeve portion ||2c of the collar H2 has a pairof axially extending slots 55 therein which cooperate with the pin lliso as to permit axial shifting of the collar but with the collar held atall times against rotation on the stern |07.

A coil spring lle of substantially conical shape has its large endseated on the flange |21) of the collar H2 and this spring acts tocontinuously urge the collar toward the right, as seen in Figs.

12 and 13, to engage the keys ||3 in the keyways H4. The small end ofthe spring H5 seats against the pin Il I and engages the rabbeted orundercut ends |||a thereof for retaining this pin in the opening l lb ofthe stem |01. The releasable connection |09 also includes a pin 15'!which is mounted in fixed relation in the end of the screw member |02 soas to project part-way into the thread groove, as shown in Figs. 14 and21, and form a stop which will engage the end convolution of the threadof the screw member 0! when the screw member |02 has traversed its slackadjusting travel.

As shown in Figs. 13 and 14 the keys ||3 are each provided with a flatface ||3a on one side thereof and an inclined face or bevel |32) on theother side thereof. The keyways IM are provided with flat side faces|1465 on both sides thereof and the flat faces at one side of thekeyways are normally engaged by the flat side faces liSc of the keys.During the slack adjusting action of the mechanism 84, the screw memberist moves relatively through the screw member iil and toward the rightas seen in Fig. 11, and when the screw member |02 reaches the end of itspermissible travel the stop pin |l will engage the end convolution ofthe thread of the screw member llii, as mentioned above. J ust prior tothis engagement, the flange |1222 of the collar H2 will engage the endface |0|a of the screw member l0! and the continued movement of thescrew member |02 to the right to engage the stop pin Hl with the endconvolution of the screw member I0! causes the collar |12 to be shiftedto the left relative to the stern |01 to thereby cause the keys ||3 tobe partially withdrawn from the keyways i4 as shown in Fig. i3. Thecomplete withdrawal of the keys from the keyways is prevented by theengagement of the stop pin H7 with the end convolution of the screwmember lili.

The partial withdrawal of the keys |13 from the keyways ||l brings theinclined faces lio of the keys to a position opposite the outer ends ofthe keyways and the tendency for the screw member |02 to be rotated bythe screw member lill will cause these inclined faces to act as cams orratchet teeth and impart further outward axial movement to the collarH2, resulting in complete disengagement of the keys from the keyways.This permits the screw member |02 to turn with the screw member mi androtate idly on the stem |07 during which time the keys cooperate withthe keyways in the manner of a ratchet and no further slack adjustingaxial movement will be imparted to the push rod When the push rod isrotated in a clockwise direction by a manual force applied to the clevisSS for the purpose of resetting the slack adjusting mechanism, thecollar ||2 will be driven by the pin lil and the partial engagement ofthe keys H3 in the keyways ||i will enable the push rod to impart aninitial return movement to the screw member |02. This initial returnmovement of the screw member 02 moves the collar H2 away from the screwmember lill thereby permitting the keys to be urged into full engagementwith the keyways by the spring H6.

The portion of the slack adjusting mechanism 86 which serves to rotatethe screw member It! for producing the slack take-up action will bedescribed next. The means for rotating this screw member comprises setsof cooperating cam elements I IS and |20 of which the cam elements l 9are carried by the xed sleeve 90 of the brake cylinder housing S2 andthe cam elements I2@ are carried by a sleeve extension |2i oi the screwmember lill. The cam elements H9 can be referred to as the cam followersand comprise rollers 22 mounted on pins |23 which are carried by thefixed sleeve de. The rollers |22 can be iormed by small anti-frictionbearings mounted on the pins |23 so that the outer races of thesebearing form the rollers. The pins |23 can be riveted or otherwise Xedin the sleeve 30 and, if desired, can be extended outwardly of thesleeve and partway through the bushing 99 for holding the latter inplace.

The cam elements are in the form of cani grooves formed in or providedon the extension sleeve |2| oi' the screw member lill. In this instancethese cam grooves are provided by mounting a pair of preformed camsegments |25 and l2 on the sleeve ifl as by means of braaing or welding.The cam grooves iZll have thrust races i2? at one side thereof which areinclined at a relatively small angle to the axis of the push rod and areformed by the edges of the cam segn ments |25 and E26. The cam groovesare provided at the other side thereof with thrust faces |28 which areinclined relative to the axis of the push rod at a much greater angle,such as an angie of about forty-five degrees, and are formed by theopposite edges of the cam segments |25 and il. [is shown in Fig. 19, thecam segments 25 and lili are relatively wide at the right hand endthereof and converge to relatively narrow linger-like portions |29 andilil at their left ends. As also shown in Fig. 19, the cam grooves ificommunicate with each other to the left of the lingers |253 and lill sothat the cam :followers lie can shift from one cam groove to the otherby passing over these finger portions, as will be explainedhereinafter'.

The sleeve extension ii which carries the cam elements |2il can beformed as an integral portion of the screw member 53| but preferably, ashere shown, is a separate member which is connected with the screwmember by a lost-motion connecting means ESI which will now bedescribed. This lost-motion connection is formed by a pair of radialpins |32 carried by the screw member and a pair of slots |33 in thesleeve member |2| into which these pins extend, as shown in Fig. 15.

rlhe slots 33 of the sleeve i2| can be reinforced cuadrangular eyeletsor ring members i3d mounted on the sleeve member in surrounding relationto the slots as shown in Fig. 19. These rcooperating pin and slotelements |32 and |33 permit limited relative rotary movement between thescrew member lill and its sleeve extension iii.

This lost-motion connection I 3l also includes a combined torsion andcompression spring |35 which is carried by a locking sleeve |35. Thetorsion spring and locking sleeve form an assembly unit, as shown inlig. 20, which is adapted to be introduced into the extension sleeve |2|by a suitable tool and engaged with the inner ends of the pins |32 forholding the latter in place. For such holding engagement with the pins|32, the locking sleeve |323 is provided with bayonet slots whichcooperate with annular grooves |38 'loi-med in the pins adjacent theirinner ends. rEhe torsion spring |35 has one end thereof anchored on thelocking sleeve |36 by means of the axially extending linger |350. of thespring engaging in a hole provided in the radial ange |360. of thissleeve. The torsion spring is provided at its other end with anoutwardly projecting finger |351) which engages in a hole of theextension sleeve |2| when the locking sleeve as senibly unit has beenassembled in place, as shown in 1ig. 15.

ln assembling the locking sleeve i3d into the position shown in Fig. 15,the torsion spring is subjected to an initial compression in an axialdirection and to an initial torsional stress, when the locking sleevehas been assembled in place the spring is maintained in this initiallystressed condition. As will be explained hereinafter, the torsion spring|35 is adapted to be subjected to further torsional stress duringrotation of the sleeve |2| in one direction and this torsional stresssubsequently rotates the sleeve in the opposite direction to shift thecam follower elements ||9 from one side to the other of the fingerportions |29 and |31) of the cam segments 25 and i.

As mentioned above, the compression spring 3? causes the return movementof the piston 83 and also causes the push rod 85 to transmit brakereleasing movement to the brake rigging. This compression spring alsocauses the slack adjust ing mechanism lll to accomplish its slacl;take-up action, as will be presently explained. One end of the spring 81seats against an end wall of the cylinder housing 82 and its other endengages a spring seat l carried by the hollow guide stem S8. The springseat li is detachably connecte with the guide stem Q3 by means of agroup oi circumferentially spaced balls |fl| which also serve totransmit the thrust of the spring directly to the outer bearing race 8d3in which the screw member itil is mounted. rThe balls ifi?. are locatedin and extend part way through openings |l2 of the guide stem 98.

The spring seat Mil includes an axially extending sleeve lfi-S havingcircumferentially spaced flared portions iil forming tapered grooves M5in which the balls lili are located. The thrust of the spring 3'! on thespring seat 40 is in a direction to cause the flared portions illll tocam the balls |46 inwardly into engagement with the bearing race 03.When the parts are in their assembled relation, as shown in Fig. 15, theballs |4| are prefertbly spaced slightly from the edges of the openings|42 so that the thrust of the spring 3l will be transmitted to the raceH13 rather than to the guide stem 93. The openings Id? are somewhatsmaller in diameter than the balls lill so that these balls will beprevented irom passing entirely through the wall of the guide stem 98when the parts are disassembled. The balls HH are prevented by thespring seat |413 from dropping out of the openings li and disengagementof the balls from the grooves irl is prevented by cotter pins l@extending across the latter.

Although the operation of the modified brake cylinder device and slackadjuster B has already `eeen partially explained herein, it will now besummarized in the following paragraphs. When application of the brakesis made, pressure iiuid is supplied to the cylinder chamber 88 cans--ing movement of the piston 33 toward the right which results in brakeapplying thrust being transmitted through the cooperating` screw menbers lill and |02 to the push rod 35 and thence to the brake riggingthrough the clevis 86. During this working stroke of the piston, thespring 81 is compressed and the sleeve extension i2i of the screw memberll is moved axially relative to the fixed sleeve Sil. During thismovement of the sleeve member |2|, the cam faces |2| of the 17 camgrooves 2G act on the cam followers i9 but since the latter are heldstationary by the sleeve e@ the resulting reaction produces rotation ofthe sleeve member 2| in a counterclockwise direction as seen in Fig 18.

This initial rotation of the sleeve member |2i is only a limitedmovement which is permitted by the slots itil of the lostmotionconnection i3! and serves to tension the torsion spring it. VIf theworking stroke of the piston is of insuicient length to cause thefingers |29 and |38 of the cam segments and 25 to move past the camfollowers H9, no slack adjusting action will take place and the torsionspring 35 will merely be alternately tensioned and relieved. by an idleback and forth limited rotation of the sleeve inem-ber |'2|. Ir" thewear which has taken place on the brake shoes or if the slack existingin the rigging is such that the working travel of the piston 853 is of alength to cause the fingers l2@ and |3il to move past the cam followersH, the torsion spring will then rotate the sleeve member lf2! in aclockwise direction to shift the cam segments 25 and |25 through anarcuate distance sufficient to cause the cam faces |28 to be presentedto the cam followers.

During the release of the brakes, the pressure is exhausted from thecylinder 88 to permit the spring 81 to causea return movement of thepiston 83. This action of the spring also causes movement of the screwmember |8| and its extensionsleeve |2| toward the left. This movement ofthe sleeve member |2| pulls the cam faces |28 against the followers H9and since the latter are held stationary by the sleeve 9c, a reactionwill result which will cause rotation of the sleeve member |2| in aclockwise direction, as seen in Fig. 18.. This rotation of the sleevemember |2I will act through the pins |32 to cause a similar rotation ofthe screw member 4| Ell and this in turn, will act on the screw member|82 to produce anoutward movement of the push rod 85 toward the right,as seen in Fig. 11, for taking up slack in the brake rigging.

When the screw member |92 has substantially traversed thev screw memberI0! so as` to bring the flange I|2b of the collar ||2 into engagementwith the end face lilla of the screw member IUI, the connection I cewith the push rod will be released, as explained above, and the screwmember 02 will then be free to rotate with the screw member IUI and nofurther slack adjusting actionwill be produced. When this conditionoccurs the slack adjusting mechanism 81E should be reset and the mannerin which this is done will be explained next.

To reset the slack adjusting mechanism 84 the brake rigging isdisconnected from the clevis 85 and the latter is rotated manually in aclockwise direction. The initial clockwise rotation of the push rod willcause the connection |09 to be reestablished and the continued rotationof the push rod will cause the screw member |02 to be screwedthrough thescrew member |0| to its initial position in which it extends into the:hollow guide stem 91 of the piston 83, as shown in Fig. 1l. Theapparatus is then ready for further slack adjusting action and the brakerigging is reconnected to the clevis 88.

To prevent the resetting operation just explained above from beingcarried too far and causing an initial movement of the piston 83, thebrake cylinder housing 82 and the clevis 86 are provided with theinterlock elements 15 and i5 which are, illustrated on av larger scalein Fig. 10

and have been described above. When these elements come into engagementthey interrupt the manual rotation of the push rod t5. The elements 75and le also accomplish another important function in the mechanisms ofFigs. l and ll in that they provide a stop for limiting the returntravel of the piston 83 during the brake releasing action. The provisionof the stop formed by the elements 'I5 and l5 thus causes the spring 8lto be confined so that the end section of the brake cylinder housing 82can be removed for inspection or replacement of the rolling sleevediaphragm 95.

From the foregoing description and the accompanying drawings it will nowbe readily understood that this invention provides an improved adjustingmechanism which is relatively simple and can be easily manufactured andassembled. It will also be seen that this invention provides a combinedbrake cylinder device and slack adjusting mechanism in which the lattermechanism is housed and protected in the brake cylinder device.Additionally, it will be. seen that when the predetermined relativetravel for taking up the slack in the brake riggingV has taken place,the take-up mechanism will be automatically rendered ineffective so asto prevent. damage to the apparatus. It will be seen further that theslack adjusting mechanism provided by this invention is adapted to bereset by manual. adjustmentk and that this manual adjustment` canbereadily accomplished from the exterior of the brake cylinder device.

Although the automatic slack adjusting mechanism, and the combined brakecylinder device and automatic slack adjuster of this invention have beenillustrated and described herein to a somewhat detailed extent, it willbe understood, of course, that the` invention is not to be regarded asbeing` limited correspondingly in scope but. includes all changes andmodifications coming within the terms of the claims hereof.

Havingthus described my invention, I claim:

l. In a slack adjuster of the character described, a housing, actuatingmeans movable axially in said housing, a push rod projecting from saidhousing, means connecting said push rod with said actuating means foractuation thereby including a screw member carried by the actuatingmeans and adapted to be rotated for causing axial movement of said pushrod relative to said actuating means and in a direction to take upslack, a sleeve connected with said housing and extending in coaxialrelation to said screw member, cooperating cam elements connectedY withsaidsleeve and screw member for imparting rotary movement to the latterin response tc operation of said actuating means in said housing, andy1ost-motion means effective to controlhthe cooperation between said camelements and embodying a torsion spring, said torsion spring beingadapted to be stressed in responsel to initial rotary movement of. saidscrew member for rendering said lost-motion means effective.

2. In a slacka-djuster, a housing, an actuating member-in saidhousingand adapted for rotary and axialmovement, a `thrust member projectingfrom said housing, a screw thread connection between said` members andadapted to cause axial movement of said thrust member for taking upslack in response torotarymovement of said actuating member, a sleeve insaid housing and extending in substantially coaxialN relation to saidkmembers, cooperating, camy elements connected with said actuating memberand sleeve and adapted to impart rotary movement to said actuatingmember in response to axial movement thereof, one oi said cam elementsbeing a follower and the other being a helical cam groove in which saidfollower engages, means connecting said sleeve with said housing so asto permit limited rotary movement of the sleeve, said cam groovecomprising one portion adapted to cooperate with said follower to causesaid limited rotary movement of said sleeve and another portion adaptedto Cooperate with said follower to cause said rotary movement of saidactuating member, and a torsion spring adapted to be tensioned by rotarymovement of said sleeve in one direction and being eiective to rotatesaid sleeve in the opposite direction for shifting the engagement forsaid follower from said one portion of said cam groove to said otherportion.

3. In a slack adjuster, a housing, a hollow actuating rod in saidhousing and adapted for rotary and axial movement, a push rod in saidactuating rod and projecting from said housing, a screw threadconnection between said rods and adapted to cause axial movement oi saidpush rod for taking up slack in response to rotary movement of saidactuating rod, a sleeve in said housing and extending in substantiallycoaxial relation to said rods, a helical cam element on said actuatingrod, a follower carried by said sleeve and engaging said element,means'iorming 'a lost-motion connection between said sleeve and housingwhich permits a limited rotary movement oi the sleeve, said cam elementhaving one portion adapted to cooperate with said follower or causingrotary movement of said sleeve in one direction and another portionadapted to cooperate with said follower for causing rotation of saidactuating rod, and a torsion spring adapted to be tensioned by therotary movement of said sleeve, said spring being eiiective whentensioned to shift said follower from engagement with said one portionof said cam element to engagement with said other portion.

4. In a slack adjusting mechanism for brakes, an actuating means adaptedfor rotary and axial movement and having a threaded portion, a push rod,a screw member on said push rod and engaging said threaded portion sothat axial movement of said actuating means imparts axial movement tosaid push rod for actuating the brakes and rotary movement of saidactuating means imparts axial movement to said push rod for taking upslack, and means connecting said screw member with said push rod so asto be held against rotation by the latter during normal operation of themechanism, said connecting means being releasable to permit rotation ofSaid screw member relative to said push rod when the screw member hassubstantially traversed said threaded portion.

5. In a slack adjusting mechanism for brakes, an actuating means adaptedfor rotary and axial movement and having a threaded portion, a push rod,a screw member on said push rod and engaging said threaded portion sothat axial movement of said actuating means imparts axial movement tosaid push rod for actuating the brakes and rotary movement of saidactuating means imparts axial movement to said push rod for taking upslack, and cooperating key and keyway means connecting said screwVYmember with said push rod so as to be held against rotation by thelatter during normal operation of the mechanism, said key means beingdisengage- 20 able from said keyway means to release said screw memberfor rotation relative to said push rod, and means adapted to causedisengagement of said key means when said screw member has substantiallytraversed said threaded portion.

5. in a slack adjusting mechanism for brakes, an actuating means adaptedfor rotary and axial movement and having a threaded portion, a push rod,a screw member on said push rod and engaging said threaded portion sothat axial movement of said actuating means imparts axial movement tosaid push rod for actuating the brakes and rotary movement of saidactuating means imparts axial movement to said push rod for taking upslack, means forming a releasable holding connection between said screwmember and said push rod by which said screw member is held againstrotation by said push rod during the normal operation of said mechanism,means adapted to cause the release oi said holding connection when saidscrew member has substantially traversed said threaded portion, andmeans eiective to reestablish said releasable holding connection.

7. In a slack adjusting mechanism for brakes, an actuating means adaptedfor rotary and axial movement and having a threaded portion, a push rod,a screw member on said push rod and engaging said threaded portion sothat axial movement of said actuating means imparts axial movement tosaid push rod for actuating the brakes and rotary movement of saidactuating means imparts axial movement to said push rod for taking upslack, means forming a releasable holding and driving connection betweensaid screw member and said push rod by which said screw member is heldagainst rotation by said push rod during the normal operation of themechanism and by which said screw member is adapted torbe rotatablydriven by the push rod during manual rotation of the latter, meansadapted to cause the release of said connection when said screw memberhas substantially traversed said threaded portion, said screw memberhaving a return travel relative to said push rod in response to themanual rotation of the latter, and means effective to reestablish saidreleasable holding and driving connection in response to the manualrotation of said push rod.

8. In a slack adjusting mechanism for brakes, a housing, an actuatingmeans adapted for rotary and axial movement in said housing and having athreaded portion, a push rod projecting from said housing, a screwmember on said push rod and engaging said threaded portion so that axialmovement of said actuating means imparts axial movement to said push rodfor actuating the brakes and rotary movement of said actuating meansimparts axial movement to said push rod for taking up slack, meansforming a releasable holding and driving connection between said screwmember and said push rod by which said screw member is held againstrotation by said push rod during the normal operation of the mechanismand by which said screw member is adapted to be rotatably driven by thepush rod during manual rotation of the latter, means adapted to causethe release of said connection when said screw member has substantiallytraversed said threaded portion, said screw member having a returntravel relative to said push rod in response to the manual rotation ofthe latter, means eective to reestablish said releasable holding anddriving connection in response to the manual rotation of said push rod,and rotary facce, rc2

Vstop means eflectivebetween saidpushrod and housing and adapted tolimitthe return relative travel of said screw member by arresting themanual rotation of'said push rod.

9. In a slack adjuster for brakes, a housing having a hollowaxialguide'projection at one end and a hollow bearing memberat its other end,actuating means axially` movable in saidhousing and' having a hollowguide stem siidable iny said guide projection, an internally threadedfirst screw member movable axially of said housing with said actuatingmeans and being rotatable in said hollow guide stem, apush rod havingone end extending into said rst screw member and its other endprojecting from said housing through said hollow bearing member, anexternally threaded second screwmemberjournaled on .said one endof saidpush rod and engaging in saidifirst screw member to'form an operatingconnection between said actuating means and said push rod adapted totransmit axial move-- ment to the latter, said operatingconnectionbeingeffective in response to relative rotary movement between said screwmembers for imparting axial movement to said push rod in a direction totake up slack, a sleeve having one end thereof in telescoping relationto said iirst screw member and its other end mounted on said hollowbearing member for limited rotary movement, cooperating cam and camfollower elements adapted to cause said relative rotary movement betweensaid screw members in response to the axial movement of said actuatingmember in one direction, one of said elements being carried by saidsleeve and the other being carried by said first screw member, meansforming a releasable holding connection adapted to hold said secondscrew member against rotation relative to said push rod during thenormal operation of the slack adjuster, and means adapted to cause therelease of said holding connection to permit rotation of said secondscrew member relative to said push rod when said second screw member hastraversed said Erst screw member.

l0. In a slack adjuster for brakes, a housing having a hollow axialguide projection at one end and a hollow bearing member at its otherend, actuating means axially movable in said housing and having a hollowguide stem slidable in said guide projection, an internally threadedfirst screw member movable axially of said housing with said actuatingmeans and being rotatable in said hollow guide stem, a push rod havingone end extending into said first screw member and its other endprojecting from said housing through said hollow bearing member, anexternally threaded second screw member connected with said one end ofthe push rod and engaging in said iirst screw member to form anoperating connection between said actuating means and said push rodadapted to transmit axial movement to the latter, said operatingconnection being effective in response to relative rotary movementbetween said screw members for imparting axial movement to said push rodin a direction to take up slack, a sleeve having one end thereof intelescoping relation to said first screw member and its other endmounted on said hollow bearing member for rotary movement, means forminga lost-motion connection between said sleeve and said hollow bearingmember including a torsion spring adapted to be tensioned by rotarymovement of said sleeve in one direction and to subsequently impartrotary movement to the sleeve in the opposite direction, and cooperatingcam and cam follower elements adapted to causev said relative lrotarymovement between said screw members inresponse to the axial movement ofsaid actuating member in one direction, one of said-elementsbeing'carried by said sleeve and the other being carried by saidfirst-screw member'.

11. In a slack adjuster, a housing, a push rod extending axially of saidhousing and projecting therefrom, actuatingA means movable in saidhousing in the direction of the axis of said push rod and including aninternally threaded'iirst screw member which is rotatableabout saidaxis, an externally threaded second screw member carried by said pushrod and engaging said rst screw member such that'rotation of-Asaid iirstscrew member will impart axial movement to said push rod'for taking upslack, av pair of sleeves in said housing extending in coaxial relationaroundsaid push rod and having their adjacent ends in telescopingrelation, one of said sleeves-having fixed connection with said housingand the other being connected with saidiirst screw member, andcooperating cam and cam follower elements carried by said sleeves andadapted to cause rotation of said rst screw member in response to axialmovements of said actuating means in one direction.

12. In a slack adjuster, a housing, a push rod extending axially of saidhousing and having one end projecting therefrom, said push rod having aspindle portion at its other end, actuating means movable in thedirection of the axis of said push rod and including an internallythreaded rst screw member which is rotatable about said axis, anexternally threaded second screw member carried by the spindle portionof said push rod and engaging said irst screw member such that rotationof said first screw member will impart axial movement to said push rodfor taking up slack, a pair of sleeves extending in coaxial relationaround said push rod and having their adjacent ends in telescopingrelation, means connecting one of said sleeves with said housing infixed relation, lost-motion means connecting the other of said sleeveswith said iirst screw member, cooperating cam and cam follower elementscarried by said sleeves and adapted to cause rotation of said iirstscrew member in response to axial movement of said actuating means inone direction, means forming a releasable holding connection adapted tohold said second screw member against rotation relative to said push rodduring the normal operation of the slack adjuster, and means adapted tocause the release of said holding connection to permit rotation of saidsecond screw member on said spindle portion when one of said screwmembers has been traversed by the other.

13. In a slack adjuster, a housing, a push rod extending axially of saidhousing and projecting therefrom, actuating means movable in saidhousing in the direction of the axis of said push rod and including aninternally threaded iirst screw member which is rotatable about saidaxis, an externally threaded second screw member carried by said pushrod and engaging said first screw member such that rotation of said rstscrew member will impart axial movement to said push rod for taking upslack, a pair of sleeves extending in coaxial relation around said pushrod and having their` adjacent ends in telescoping relation, meansconnecting one of said sleeves with said housing in fixed relation,lost-motion means connecting the other of said sleeves with said firstscrew member, and cooperating cam and cam follower elements carried bysaid sleeves and adapted to cause rotation of said rst screw member inresponse to axial movement of said actuating stems in slidableengagement with said xed 1 sleeve and said guide projection, a push rodhaving one end thereof projecting from said housing through said xedsleeve and its other end extending into said hollow guide projection, aninternally threaded first screw member connected with said actuatingmeans, an externally threaded second screw member connected with saidpush rod and engaging in said rst screw member, said screw membersforming a thrust transmitting connection between said actuating meansand said push rod and said push rod being axially movable for taking upslack in response to rotation of said first screw member, and cam andcam follower elements connected with said xed sleeve and said firstscrew member and cooperating to produce rotation of the latter inresponse to axial movement of said actuating means in one direction.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 685,380 Johnson Oct. 29, 1901 728,443 Clark May 19, 1903951,577 Price Mar. 8, 1910 1,180,097 Woods Apr. 18, 1916 1,755,305Osborn Apr. 22, 1930 2,003,769 Christenson June 4, 1935 2,089,491 KuiperAug. 10, 1937 2,160,859 Grayson June 6, 1939 2,246,873 Browall June 24,1941

